Drag-reducing shaft tailfin for vehicles

ABSTRACT

A streamlined tailfin pivotably attached to a shaft-shaped member disposed on a vehicle provides for reduced drag in winds varying in direction impinging thereon.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of patent application Ser. No.16/727,005, filed Dec. 26, 2019, which is a continuation of patentapplication Ser. No. 15/593,996, filed May 12, 2017, which is acontinuation of patent application Ser. No. 13/799,005, filed Mar. 13,2013, which claims the benefit of provisional patent application No.61/745,357, filed Dec. 21, 2012 by the present inventor.

BACKGROUND OF THE INVENTION Field of the Invention

The present embodiment relates to vehicle wheels, and particularly toshields and devices used to reduce drag on rotating vehicle wheels.

Description of Related Art

Inherently characteristic of rotating vehicle wheels, and particularlyof spoked wheels, aerodynamic resistance, or parasitic drag, is anunwanted source of energy loss in propelling a vehicle. Parasitic dragon a wheel includes viscous drag components of form (or pressure) dragand frictional drag. Form drag on a wheel generally arises from thecircular profile of a wheel moving though air at the velocity of thevehicle. The displacement of air around a moving object creates adifference in pressure between the forward and trailing surfaces,resulting in a drag force that is highly dependent on the relative windspeed acting thereon. Streamlining the wheel surfaces can reduce thepressure differential, reducing form drag.

Frictional drag forces also depend on the speed of wind impingingexposed surfaces, and arise from the contact of air moving oversurfaces. Both of these types of drag forces arise generally inproportion to the square of the relative wind speed, per the dragequation. Streamlined design profiles are generally employed to reduceboth of these components of drag force.

The unique geometry of a wheel used on a vehicle includes motion both intranslation and in rotation; the entire circular outline of the wheeltranslates at the vehicle speed, and the wheel rotates about the axle ata rate consistent with the vehicle speed. Form drag forces arising fromthe moving outline are apparent, as the translational motion of thewheel rim must displace air immediately in front of the wheel (andreplace air immediately behind it). These form drag forces arisingacross the entire vertical profile of the wheel are therefore generallyrelated to the velocity of the vehicle.

As the forward profile of a wheel facing the direction of vehicle motionis generally symmetric in shape, and as the circular outline of a wheelrim moves forward at the speed of the vehicle, these form drag forcesare often considered uniformly distributed across the entire forwardfacing profile of a moving wheel (although streamlined cycle rims canaffect this distribution somewhat). This uniform distribution ofpressure force is generally considered centered on the forward verticalwheel profile, and thereby in direct opposition to the propulsive forceapplied at the axle, as illustrated in FIG. 24.

However, as will be shown, frictional drag forces are not uniformlydistributed with elevation on the wheel, as they are not uniformlyrelated to the speed of the moving outline of the wheel rim. Instead,frictional drag forces on the wheel surfaces are highly variable anddepend on their elevation above the ground. Frictional drag must beconsidered separate from form drag forces, and can be more significantsources of overall drag on the wheel and, as will be shown, thereby onthe vehicle.

The motion of wheel spokes through air creates considerable drag,especially at higher relative wind speeds. This energy loss isparticularly critical in both bicycle locomotion and in high-speedvehicle locomotion. Previous efforts to reduce this energy loss inbicycle wheels have included bladed-spoke designs; the addition ofvarious coverings attached directly to the wheel; and the use of deeper,stiffer, and heavier aerodynamic rims. As winds, and particularlyheadwinds, are a principal source of energy loss in bicycle locomotion,expensive aerodynamic wheel designs have become increasingly popular.However, these aerodynamic wheel designs have often been tuned to reduceform drag, rather than frictional drag. As a result, augmentedfrictional drag forces present on these larger-surfaced aerodynamicwheel designs tend to offset much of the gains from reduced form dragforces, thereby negating potential reductions in overall drag.

Bladed spokes, tapered in the direction of motion through the wind, aredesigned to reduce form drag. These streamlined spokes suffer fromincreased design complexity, increased weight and higher costs. Inaddition, such bladed designs are more susceptible to crosswind drageffects: The increased surface area of the bladed spoke can rapidlyincrease form drag in the presence of any crosswind; any crosswinddirected upon the flat portion of the spoke quickly increases pressuredrag upon the spoke.

Under low crosswinds, the bladed spoke presents a relatively smallforward profile facing oncoming headwinds, minimizing form drag. Indeed,the thin profile of the blade generally minimizes form drag over that ofround spoke profile. However, most external winds will not be preciselyaligned co-directional with the forward motion of the wheel. Such windscause a crosswind component to be exerted upon the wheel, leading toflow-separation—and thus turbulence—behind the bladed spoke, and therebygenerally negate the potential aerodynamic benefit of the bladed-spokedesign. Under high crosswinds, the round spoke profile may evenoutperform the bladed spoke in terms of drag reduction. Perhaps a resultof these conflicting factors, the bladed spoke has not become the commonstandard for use in all bicycle competitions.

Wheel covers generally include a smooth covering material attacheddirectly to the wheel over the outside of the spokes, generally coveringa large portion of the wheel assembly, often extending from the wheelrim to the axle. Wheel covers add weight to the wheel assembly and canresult in more wheel surface area being exposed to winds. The additionalweight on the wheel is detrimental to wheel acceleration, while thelarge surface area of the cover can increase frictional drag. Althoughcovering the wheel spokes can reduce form drag forces thereon, theincreased frictional drag forces on the larger surface areas can largelyoffset any aerodynamic benefit. In addition, covering large portions ofthe wheel also increases bicycle susceptibility to crosswind forces,destabilizing the rider. For this reason, wheel covers are generallyused only on the rear wheel of a bicycle, and generally only under lowcrosswind conditions. Perhaps as a result of these conflicting factors,wheel covers have not become the standard equipment for use in allbicycle competitions.

Recently developed for use on bicycles, deeper, stiffer and heavieraerodynamic wheel rims suffer several drawbacks: deeper (wider along theradial direction of the wheel) and streamlined rims are often used toreduce profile drag on high-performance bicycle wheels. As mentioned,these rims are generally designed to reduce profile drag under variouscrosswind conditions. However, these deeper rims—having generally largerrotating surface areas—can dramatically increase friction drag. As willbe shown, friction drag is particularly increased on the expanded upperwheel surfaces, largely negating any potential benefit of the reducedprofile drag. In addition, such deep wheel rims with minimal spokes mustbe made stronger and stiffer—typically with double-wallconstruction—than conventional single-wall, thin-rim designs. As aresult, such deep rims often ride more harshly over bumpy terrain, andare generally heavier, adding weight to the bicycle, which becomes adrawback when the grade becomes even slightly uphill.

As a result of these and other countervailing factors, no single wheeldesign has emerged as the preferred choice for reducing drag on bicyclewheels over a wide range of operating conditions. Instead, a variety ofwheel designs are often employed in modern racing bicycles. In the samecompetition, for example, some riders may choose to use bladed spokes,while others choose round spokes, while still others choose deep rims orwheel covers. The differences in performance between these various wheeldesigns appear to only marginal affect the outcome of most races.

In sports cars, wheel covers have been employed to reduce aerodynamicvortices from developing inside the inner wheel assembly. These coverssmooth the air flowing over the outer wheel and deflect a portion of theair to the brake linings, providing cooling thereon. In addition,various wings attached to the body of the car have been employed todeflect air around the drag-inducing exposed wheels. Such wings aregenerally located low to the ground, and are often configured to deflectair to one side or the other of exposed wheels, or to provide vehicledown-forces to counteract significant lifting forces generated by theexposed wheels. As will be shown, use of these wings to deflect airupwards onto the upper wheel can actually augment the down forceproblem, as well as contribute to more overall vehicle drag. And relatedflip-up deflectors have been incorporated into the body molding of somesports cars, although these have been generally limited to placement infront of the semi-exposed rearmost wheel. Such flip-up deflectors havealso been used to augment down-forces in order to enhance vehiclestability at high speeds.

In various cycles, fenders and mud-covers have been used to cover wheelsfor other purposes. However, these items are generally oriented on thecycle consistent with their intended purpose of shielding the rider fromdebris ejected from the wheel. As such, they are not necessarilydesigned to be either forwardly positioned, nor closely fitted to thetire and wheel for aerodynamic shielding purposes. On some bicycles,skirt guards have been employed specifically to prevent clothing of therider from becoming entangled with the rotating wheel. However, theseguards are often made of porous construction, and are generally employedon the rear-most wheel, rather than on the front-most wheel, where thepotential aerodynamic benefit is generally greater.

Perhaps because aerodynamic devices are generally not allowed by rulesgoverning many bicycle competitions, development of fairings forbicycles remains somewhat limited. Instead, fairings have been generallyused to cover either the entire cycle, or the broad front area of thecycle, shielding both rider and cycle. Enclosing-type fairings typicallyhave quite large surface areas, which augment frictional drag forces,largely negating any benefit in reducing form drag from streamlining theforward profile of the bicycle. Nevertheless, numerous bicycle speedrecords have been achieved using these larger fairings, validating theireffectiveness. Frontal wind-deflecting fairings are typically used toreduce form drag on various components on a cycle; however, theirgreatly expanded surface areas can minimize their effectiveness byintroducing greater frictional drag. The potential effectiveness ofusing smaller fairings—having minimal form and friction drag—forshielding specific, critical, drag-sensitive areas of moving wheelsurfaces has not been properly recognized.

A study by Sunter and Sayers (2001), Aerodynamic Drag Mountain BikeTyres, Sports Engineering, 4, 63-73, proposed and tested the use of afront-mounted wind-deflector fender for relatively low-speed,rough-surfaced, down-hill racing mountain bicycle front wheels. However,as will be shown, the tested fender was unnecessarily extensive; itsextended design—covering the tire to well below the level of theaxle—failed to focus properly on key sources of drag on a typicalbicycle wheel. Instead, in this investigation, variations in drag weremeasured with differing tire tread patterns, and differing fenderclearances, using knobby mountain bike tires, and were measured on thefront wheel only. Moreover, sufficient fender clearances with the tirewere investigated, with the aim of determining any potential benefit inreducing drag on the bicycle against the potential mud accumulationthere-between.

Referencing an earlier study, Kyle (1985) Aerodynamic Wheels. Bicycling,December, 121-124, in this later study, Sunter and Sayers noted a 30%increase in drag on a wheel rotating with a speed equivalent to theexposed headwind, versus a stationary wheel exposed to the sameheadwind. As reported, this measurement seems to have represented theincrease in torque needed to rotate the wheel about the axle. However,the change in torque measured about the axle on a fixed wheel mounted inan air-stream—as will be shown—cannot be considered an accuraterepresentation of the change in drag force required to propel thebicycle. Torque measured this way is only an indirect factor needed todetermine the effects on overall bicycle drag. As will be shown, the netdrag force is generally not well centered on the rotating bicycle wheel,causing drag forces on the upper wheel to be magnified. Indeed, theoffset drag force on the wheel contributes significantly more to overallbicycle drag than commonly understood.

A number of studies of bicycle wheel drag measured in wind tunnels alsofail recognize the importance of drag forces on the upper wheel. Testsare typically conducted with the wheel suspended in the airstream, withthe drag on the wheel measured via force gauges attached to thesuspension arm. As will be shown, the magnification of upper wheel dragforces occurs when the wheel is in contact with the ground. Measuringdrag on wheels suspended in an airstream will yield incomplete results,particularly for application to moving vehicles.

For example, an earlier study by Greenwell et al, Aerodynamiccharacteristics of low-drag bicycle wheels, Aeronautical Journal, 1995,99, 109-120, measured translational drag on a wheel suspended from atorsion tube in a wind tunnel, where the wheel was driven by a motor andmade no contact with a ground plane. They concluded that in thisconfiguration—unexpectedly—rotational speed had little influence on thetranslational drag force directed upon the wheel assembly.

In a more recent study, Moore and Bloomfield, Translational androtational aerodynamic drag of composite construction bicycle wheels,Proceedings of the Institution of Mechanical Engineers, Part P: Journalof Sports Engineering and Technology Jun. 1, 2008, vol. 222, no. 2,91-102, the measured drag was extended to include rotational drag on thewheel. However, this study also failed to include a ground plane incontact with the wheel; the wheel remained suspended wind tunnel. Asmentioned, this configuration does not accurately reflect the totalretarding force upon a vehicle in motion caused by drag forces on thewheel.

Sunter and Sayers also failed to recognize the magnifying effect that anoff-center net drag force on the wheel can have on overall bicycle drag.Instead, they concluded that with the modest improvement in drag torquemeasured upon the rotating wheel using the wind-deflecting fender, onlycorresponding modest improvement in overall bicycle drag could beexpected. They further concluded that the use of extensive front-wheelwind-deflecting fenders—having a rather large forward profiles—mightthus prove beneficial in the specific application of mountain bicycledownhill racing, where only modest reductions in overall drag mightyield a winning advantage in higher speed races. This conclusion wouldbe consistent with the faulty observation that total drag forces aregenerally well centered on the wheel.

It has long been recognized that minimizing drag on large trucks andtheir trailers has significant potential for improving fuel economies.Extensive wind deflectors have been used in front of the rear wheels onextended truck trailers, but are generally designed to deflect verylarge volumes of air to the either side of the rear wheels. Deflectingunnecessary volumes of air with large fairings, can produce significantform drag by the fairing itself, thereby negating much of the intendedbenefit in reducing wheel drag. And as will be shown, deflecting airbelow the level of the axle can be particularly detrimental in reducingoverall vehicle drag.

For example, in patent US 2010/0327625A1, a V-shaped air deflector isshown positioned in front of a wheel for the purpose of deflecting largevolumes of air to either side in order to reduce wheel drag. However,the deflector shown is unnecessarily large, introducing substantial formdrag. And the deflector is positioned centered at the elevation of theaxle, extending symmetrically above and below the axle. As mentioned,deflecting air onto lower surfaces of the wheel can be detrimental toreducing overall drag on the vehicle. And as shown, the deflector failsto fully shield the most critical drag-inducing uppermost surfaces ofthe wheel.

In U.S. Pat. No. 6,974,178B2, the deflectors shown are simplyunnecessarily large, again introducing substantial form drag.

Other examples in the art also deflect air downward onto the lowersurfaces of the wheel, thereby negating much of the intended aerodynamicbenefit. These include trailer wheel deflectors of US 2010/0066123A1,U.S. Pat. Nos. 4,640,541, 4,486,046 and 4,262,953.

Other examples in the art also shield headwinds from lower surfaces ofthe wheel below the axle, thereby also negating much of the intendedaerodynamic benefit. These include fairings of US 2011/0080019A1, U.S.Pat. No. 7,520,534B2, U.S. Pat. No. 7,322,592B2, U.S. Des. 377,158, U.S.Pat. Nos. 5,348,328, 4,773,663, 4,411,443, 4,326,728 and 2,460,349.

Wheel fairings often used on light aircraft are generally designed forreduced form drag of the wheel assembly while airborne, and generallycover the upper wheel to well below the axle. An example is shown inU.S. Pat. No. 4,027,836. Wheel pants designed as mud covers forshielding wings from ejected debris are also seen in the art, showing anupper wheel fender designed with extensive streamlined surfaces oftenextending substantially above and behind the wheel. As will be shown,such designs are not optimized for terrestrial use, either by extendingbelow the level of the axle, or by not optimally shielding the mostcritical drag-inducing surfaces of the upper wheel.

Other examples in the art show skirt guards on the rear wheel of cycles,where the potential aerodynamic benefit is considerably less than thatof the front wheel. These include guards of U.S. D634,2495, U.S. Pat.Nos. 3,101,163 and 1,027,806. And fender of patent U.S. D612,781S is notshown mounted on a vehicle.

Spoke art includes many examples having rectangular or otherwisenon-aerodynamic cross-sectional profiles of wheel spokes for use inautomotive applications. Examples include patents U.S. D460,942, U.S.D451,877, U.S. D673,494, U.S. D396,441 and others.

Cycle spoke art includes a tapered spoke of U.S. Pat. No. 5,779,323where the cross-sectional profile of the spoke changes from more highlyelliptical near the wheel hub to more generally oval near the wheel rim.As will be shown, the spoke shown is tapered to minimize—rather thanmaximize—any aerodynamic benefit, especially when used in the presenceof crosswinds.

Tires are generally designed with tread patterns intended to maximizetraction with the road surface and to minimize rolling friction and roadnoise. A wide variety of tread patterns exist, each designed forspecific vehicle applications. Some tires with aggressive tread patternsare designed for maximum traction in off-road conditions. These tiresgenerally have square or rectangular lugged patterns in the tread, andsuffer from increased road noise and wind resistance. The need for tireswith aggressive tread patterns specifically designed to reduce drag onthe vehicle have been largely overlooked.

For example, in US patent 2007/0151644 A1, an oval-shaped tread patternis shown. While oval shaped tread lugs have the potential to reducedrag, their closely spaced pattern shown diverts most of the air to flowover the top surfaces of the tire, rather than between the lugs.Moreover, the closely spaced oval lugs are designed to reduce stressesduring tire compression—thereby improving the rolling resistance of thetire—and to reduce the incidence of trapping stones between the lugs. Assuch, the minimally spaced lugs are an essential characteristic of thisembodiment. As disclosed, any minor improvement in the aerodynamiccharacteristics of the tire was not included.

BRIEF SUMMARY OF THE INVENTION

A related embodiment comprises an aerodynamically optimized wheel covershielding critical upper drag-inducing wheel surfaces from headwinds,thereby reducing the total drag-induced resistive forces upon the wheelassembly and minimizing needed vehicle propulsive counter-forces.

A related embodiment comprises an aerodynamically optimizedwind-deflecting fairing shielding critical upper drag-inducing wheelsurfaces from headwinds, thereby reducing the total drag-inducedresistive forces upon the wheel assembly and minimizing needed vehiclepropulsive counter-forces.

A related embodiment comprises a vehicle engine exhaust pipe disposed tocause ejected exhaust gases to deflect headwinds to shield criticalupper drag-inducing wheel surfaces, thereby reducing the totaldrag-induced resistive forces upon the wheel assembly and minimizingneeded vehicle propulsive counter-forces.

A related embodiment comprises an automotive spoked wheel havingstreamlined oval-shaped wheel spokes, arranged in one or more transverserows for enhanced axial strength, thereby reducing the totaldrag-induced resistive forces upon the wheel assembly and minimizingneeded vehicle propulsive counter-forces.

A present embodiment comprises a streamlined tailfin rotatably attachedto a wheel spoke, pivotable about the spoke in response to varyingcrosswind conditions, thereby reducing potential turbulent flowseparation behind the spoke and tailfin due to crosswinds, and therebyreducing the total drag-induced resistive forces upon the wheel assemblyand minimizing needed vehicle propulsive counter-forces.

A related embodiment comprises a cycle wheel spoke tapered from astreamlined blade or highly elliptical cross-sectional profile nearestthe wheel rim for reduced drag from higher speed headwinds, to a morecircular cross-sectional profile nearest the wheel central hub where therelative crosswind components are higher, thereby minimizing potentialdrag-induced turbulent flow separation behind spoke surfaces along theentire length of the spoke, and thereby reducing the total drag-inducedresistive forces upon the wheel assembly and minimizing needed vehiclepropulsive counter-forces.

A related embodiment comprises tire having aerodynamically optimizedtread blocks diposed in an aerodynamically optimized pattern, reducingdrag from headwinds on critical upper drag-inducing tire surfaces, andthereby reducing the total drag-induced resistive forces upon the wheelassembly and minimizing needed vehicle propulsive counter-forces.

A present embodiment comprises a method for optimally minimizing thetotal drag-induced resistive forces upon the wheel assembly of avehicle, and thereby minimizing needed vehicle propulsivecounter-forces.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

While one or more aspects pertain to most wheeled vehicles not otherwisehaving fully shielded wheels that are completely protected from oncomingheadwinds, the embodiments can be best understood by referring to thefollowing figures.

FIG. 1 is a front cycle wheel assembly, as typically found on a bicycleor motorcycle, where a fairing is attached and positioned as shown toeach interior side of the fork assembly, thereby shielding the upper-and front-most surfaces of the spoked wheel from oncoming headwinds.

FIG. 2 is a front cycle wheel assembly, as typically found on a bicycleor motorcycle, where a fender is attached and positioned as shown to thefork assembly, thereby shielding the upper- and front-most surfaces ofthe tire and wheel rim from oncoming headwinds.

FIG. 3 is a front cycle wheel assembly, as typically found on a bicycleor motorcycle, where a combination fender and fairing assembly isattached and positioned as shown to the fork assembly, thereby shieldingthe upper- and front-most surfaces of the tire, wheel rim and spokedinner-wheel structure from oncoming headwinds.

FIG. 4 is a vehicle wheel assembly, as typically found on a sports car,where a fender is attached and positioned as shown to the wheelsuspension assembly, thereby shielding the upper- and front-mostsurfaces of the tire from oncoming headwinds.

FIG. 5 is a vehicle wheel assembly, as typically found on a sports car,where a fender and fairing assembly is attached and positioned as shownto the wheel suspension assembly, thereby shielding both the upper- andfront-most surfaces of the tire, and the upper inner-wheel structurefrom oncoming headwinds.

FIG. 6 is a vehicle wheel assembly, as typically found on a sports car,where a fairing assembly is attached either to the wheel suspensionassembly or to the car body structure, and positioned as shown,deflecting upward any wind impinging thereon, and thereby shielding boththe upper- and front-most surfaces of the tire from oncoming headwinds.

FIG. 7 is a front cycle wheel assembly, as typically found on a bicycleor motorcycle, where a fairing is attached and positioned as shown toeach side of the fork assembly, and where said fairing includes amovable lower section, which may be adjusted to expand or collapse thetotal surface area of the fairing to accommodate a range of crosswindconditions.

FIG. 8 shows an example of prior art for automotive spoked wheels withminimal spokes, as typically found on modern automobiles, illustratingthe typical square profile of the spokes, which increases drag oncritical rotating wheel surfaces.

FIG. 9 shows an example of prior art for automotive spoked wheels withmany outwardly-positioned spokes, as typically found on high-performancesports cars, illustrating the typical rectangular profile of the spokes,which increases drag on critical rotating wheel surfaces.

FIG. 10 shows the drag-inducing, rectangular cross-sectional profiletypical of prior-art spokes used in automotive wheels, as illustrated inFIGS. 8 and 9.

FIG. 11 shows the streamlined, drag-reducing, oval-shapedcross-sectional profile of a spoke to be used in one or more of theembodiments, including automotive wheels.

FIG. 12 shows an automotive wheel with these streamlined, drag-reducing,oval cross-sectional shaped spokes, thereby reducing drag on criticalrotating wheel surfaces.

FIG. 13 shows an automotive wheel with these streamlined, drag-reducing,oval cross-sectional shaped spokes, thereby reducing drag on criticalrotating wheel surfaces. Two rows of spokes are shown, slightly offsetaxially from each other, thereby increasing the strength of the wheel inthe transverse direction.

FIG. 14 shows the tapered, drag-reducing cross-sectional profile of aspoke fin installed on a typical round wire spoke, where the spoke finis free to swivel about the spoke and thereby to adjust to varyingcrosswind influences as the wheel rotates.

FIG. 15 shows a short section of the tapered, drag-reducing fininstalled on a typical round wire spoke, where the spoke fin is free toswivel about the spoke and thereby to adjust to varying crosswindinfluences as the wheel rotates.

FIG. 16 shows several sections of spoke fins installed on a typicalround wire spoke, where each spoke fin is free to swivel about the spokeindependently, and thereby to adjust to varying crosswind influences asthe wheel rotates. This fin design could also be used on a vehicle radioantenna, reducing drag and thereby improving fuel consumption forvehicles, especially when operating at highway speeds.

FIG. 17 shows a plot of calculated average moments—about the groundcontact point—of drag force, that are exerted upon rotating wheelsurfaces as a function of the elevation above the ground. The relativedrag forces are determined from calculated wind vectors for the rotatingsurfaces on a wheel moving at a constant speed of V, and plotted forseveral different wind and wheel-surface shielding conditions.Specifically, relative magnitudes in average drag moments about theground contact point as a function of elevation are plotted, for eightconditions: comparing with (dashed lines) and without (solid lines)shielding covering the upper third of wheel surfaces, for tailwindsequal to half the vehicle speed; for null headwinds; for headwinds equalto half the vehicle speed; and for headwinds equal to the vehicle speed.The rising solid curves plotted show the highest moments to be near thetop of the wheel, while the dashed curves show the effect of the uppershield in substantially reducing the average drag moments on therotating wheel.

FIG. 18 shows a plot of calculated relative drag torque exerted uponrotating wheel surfaces as a function of elevation above the ground. Therelative total drag torques are determined from the calculated averagemoments in combination with the chord length at various elevations on awheel moving at a constant speed of V, for several different wind andwheel-surface shielding conditions. Relative magnitudes in total dragtorque about the ground contact point as a function of elevation areplotted for eight conditions: comparing with (dashed lines) and without(solid lines) shielding covering the upper third of wheel surfaces, fortailwinds equal to half the vehicle speed; for null headwinds; forheadwinds equal to half the vehicle speed; and for headwinds equal tothe vehicle speed. The areas under the plotted curves represent thetotal torque from frictional drag on wheel surfaces. Comparing thedifferences in area under the plotted curves reveals the general trendof the upper shield to substantially reduce the total drag torque on therotating wheel.

FIG. 19 shows a tapered spoke for use on a typical racing bicycle wheel.The spoke is shown tapering from a highly elliptical cross-sectionalprofile located nearest the wheel rim—shown at the top of the figure—toa more circular cross-sectional profile located on the spoke nearest thewheel central hub—shown at the bottom of the figure.

FIG. 20 shows a side view of the tapered spoke of FIG. 19.

FIG. 21 shows the highly elliptical cross section A-A of the taperedspoke shown in FIGS. 19 and 20.

FIG. 22 shows the more oval cross section B-B of the tapered spoke shownin FIGS. 19 and 20.

FIG. 23 shows the near circular cross section C-C of the tapered spokeshown in FIGS. 19 and 20.

FIG. 24 is a diagram of a wheel rolling on the ground representingtypical prior art models, showing the net pressure drag force (P)exerted upon the forward wheel vertical profile—which moves at the speedof the vehicle—being generally centered near the axle of the wheel andbalanced against the propulsive force (A) applied at the axle.

FIG. 25 is a diagram of a wheel rolling on the ground, showing the netfriction drag force (F) upon the wheel surfaces—which move at differentspeeds depending on the elevation from the ground—being offset from theaxle and generally centered near the top of the wheel. A ground reactionforce (R)—arising due to the drag force being offset near the top of thewheel—is also shown. The force (A) applied at the axle needed toovercome the combination of drag forces (F+P) and reaction force (R) isalso shown.

FIG. 26 shows a tire with an off-road tread pattern typical of priorart, having relatively sharp, angular, non-aerodynamic both windward-and leeward-facing sides on each tread block.

FIG. 27 shows an aerodynamic tread pattern with aggressive tread blockshaving relatively sharp, angular, non-aerodynamic windward-facing sidesfor traction, and more smooth and streamlined leeward-facing sides forminimizing drag. The tread blocks are shown separated and offsetlongitudinally in order to partially redirect air flowing from the frontleading surface of one block toward the rear trailing surface of anadjacent block, thereby reducing pressure drag on the adjacent block.

FIG. 28 shows an aerodynamic tread pattern with aggressive tread blockshaving relatively sharp, angular, non-aerodynamic windward-facing sidesfor traction, and more smooth and streamlined leeward-facing sides forminimizing drag. The tread blocks are show separated and offsetlongitudinally in an oblique arrangement, in order to partially redirectair flowing from the front leading surface of one block toward the reartrailing surface of an adjacent block—thereby reducing pressure drag onthe adjacent block—and toward the outside of the tire.

FIG. 29 shows an aerodynamic tread pattern with aggressive tread blockshaving oval-shaped tread blocks oriented with wider sides positionedlaterally for more traction, while having a substantially streamlinedprofiles for minimizing drag. Such a symmetrical tread pattern allowsfor bi-directional mounting on a vehicle. The tread blocks are shownseparated and offset sufficiently in order to partially redirect airflowing from the front leading surface of one block toward the reartrailing surface of an adjacent block, thereby reducing pressure drag onthe adjacent block.

FIG. 30 shows an aerodynamic tread pattern with aggressive tread blockshaving oval-shaped tread blocks oriented with wider sides positionedlongitudinally for more drag reduction, and having a substantiallystreamlined profiles for minimizing drag. Such a symmetrical treadpattern allows for bi-directional mounting on a vehicle. The treadblocks are shown separated and offset sufficiently in order to partiallyredirect air flowing from the front leading surface of one block towardthe rear trailing surface of an adjacent block, thereby reducingpressure drag on the adjacent block.

FIG. 31 shows prior art of a typical top-fuel dragster race-car havingengine exhaust pipes arranged in a linear array to direct exhaust gasessubstantially to the outside of the rear wheel assembly.

FIG. 32 shows a typical top-fuel dragster race-car having engine exhaustpipes arranged in a distributed array to direct exhaust gases directlyabove the rear wheel assembly, spanning the zone shielding the entirewidth of the upper surfaces of the wide tire.

FIG. 33 shows a cross section of one-half of an automotive wheelassembly having nonparallel rows of aerodynamic spokes for strengtheningthe wheel in the axial direction.

DETAILED DESCRIPTION OF THE INVENTION

Various embodiments are described below in detail, each with meansproviding a reduction in drag on the wheel assembly of a vehicle. Assuch, each may considered as one embodiment of a comprehensive categoryof embodiments, whose scope is limited to that defined herein, and laterreferred thereto as: drag reduction means.

Furthermore, embodiments depicted in FIGS. 1, 2, 3, 4, 5 and 7 aredescribed below and belong to a comprehensive category of embodiments,whose scope is limited to that defined herein, and later referredthereto as: wheel cover.

First Embodiment—Description—FIG. 1

As shown in FIG. 1, a streamlined fairing 1 is attached to the inside ofa front fork tube assembly 2 of a typical bicycle 3 having spoked wheels4. The fairing 1 is positioned closely adjacent to the inside structureof wheel 4, covering much of the upper and front-most quadrant of thewheel 4 as shown, and is rigidly fixed to front-fork tube assembly 2using fastener 11 and strut 10. While only one fairing 1 is shown, theembodiment will generally include a similar fairing 1 located on theopposite side of the wheel 4, thereby shielding the entire upper innerstructure of wheel 4 from the oncoming wind caused by forward motion ofcycle 3. The fairing 1 has sufficient structural rigidity to allow closeplacement to spokes 5 and rim 6 of the wheel 4, thereby minimizingoncoming wind from leaking into the inner structure of wheel 4.

With fairing 1 configured in this way, the spokes 5 positioned near thetop of the wheel 4 are shielded from headwinds. Shielded in this way,the topmost spokes 5 are moving at an effective wind speed generallyless than or equal to the ground speed of the cycle 3, rather thanmoving at an effective headwind speed of up to nearly twice the groundspeed of cycle 3. As a result, the aerodynamic drag forces exerted uponthe topmost spokes 5 are greatly reduced.

The reduction in drag force due to fairing 1 is generally greater nearthe top of the wheel 4, where the spokes 5 are moving fastest withrespect to headwinds otherwise impinging thereupon. As uppermost spokes5 rotate away from the topmost point to an intermediate position withrespect to either of the two lateral mid-points at the height of theaxle on the wheel 4, these headwind drag forces are greatly reduced.

The embodiment shown in FIG. 1 includes a minimal fairing 1 positionedclosely adjacent to the wheel, and shielding generally the most criticalupper and forward-oriented quadrant of wheel 4, minimizing the additionof unnecessary weight or drag-inducing structure to cycle 3. The fairing1 shown extends sufficiently rearward to provide a measure of profileshielding of the rear portion of the wheel and spokes, diverting thewind from impinging directly the rear rim of the wheel, and therebypermitting a generally streamlined flow to be maintained across theentire upper section of wheel assembly.

First Embodiment—Operation—FIGS. 1, 17, 18, 23 and 24

The shielding provided by fairing 1 is particularly effective sinceaerodynamic forces exerted upon exposed vehicle surfaces are generallyproportional to the square of the effective wind speed impingingthereon. Moreover, the power required to overcome these drag forces isgenerally proportional to the cube of the effective wind speed. Thus, itcan be shown that the additional power required to overcome these dragforces in propelling a vehicle twice as fast over a fixed distance, inhalf the time, increases by a factor of eight. And since this powerrequirement is analogous to rider effort—in the case of a bicyclerider—it becomes critical to shield the most critical drag-inducingsurfaces on a vehicle from oncoming headwinds.

In any wheel used on a vehicle, and in the absence of any externalheadwinds, the effective horizontal wind speed at a point on the wheelat the height of the axle is equal to the ground speed of the vehicle.Indeed, the effective headwind speed upon any point of the rotatingwheel depends on that point's current position with respect to thedirection of motion of the vehicle.

Notably, a point on the moving wheel coming into direct contact with theground is necessarily momentarily stationary, and therefore is notexposed to any relative wind speed, regardless of the speed of thevehicle. While the ground contact point can be rotating, it is nottranslating; the contact point is effectively stationary. And points onthe wheel nearest the ground contact point are translating with onlyminimal forward speed. Hence, drag upon the surfaces of the wheelnearest the ground is generally negligible.

Contrarily, the topmost point of the wheel assembly (opposite theground) is exposed to the highest relative wind speeds: generally atleast twice that of the vehicle speed. And points nearest the top of thewheel are translating with forward speeds substantially exceeding thevehicle speed. Thus, drag upon the surfaces of the upper wheel can bequite substantial. Lower points on the wheel are exposed to lessereffective wind speeds, approaching a null effective wind speed—and thusnegligible drag—for points nearest the ground.

Importantly, due to the rotating geometry of the wheel, it can be shownthat the effective combined frictional drag force exerted upon the wheelis typically centered in closer proximity to the top of the wheel,rather than centered closer to the axle as has been commonly assumed inmany past analyses of total wheel drag forces. While the net pressure(or form) drag (P) force on the forwardly facing profile of the wheel isgenerally centered with elevation and directed near the axle on thewheel (as shown in FIG. 24), the net frictional drag force (F) upon themoving surfaces is generally offset to near the top of the wheel (asshown in FIG. 25).

Indeed, it is near the top of the wheel where the relative winds areboth greatest in magnitude, and are generally oriented most directlyopposed to the forward motion of rotating wheel surfaces. Moreover, inthe absence of substantial external headwinds, the frictional dragexerted upon the lower wheel surfaces contributes relatively little tothe net drag upon the wheel, especially when compared to the drag uponthe upper surfaces. The combined horizontal drag forces (from pressuredrag from headwinds deflected by both the leading and trailing wheelforwardly facing profiles, and from frictional drag from headwindsimpinging upon the forwardly moving surfaces) are thus generallyconcentrated near the top of the wheel under typical operatingconditions. Moreover, with the faster relative winds being directedagainst the uppermost wheel surfaces, total drag forces combine near thetop to exert considerable retarding torque upon the wheel.

As mentioned, the horizontal drag forces are primarily due to bothpressure drag forces generally distributed symmetrically across theforwardly facing vertical profiles of the wheel, and to winds infrictional contact with moving surfaces of the wheel. Pressure dragforces arise primarily from the displacement of air from around theadvancing vertical profile of the wheel, whose circular outline moves atthe speed at the vehicle. As discussed above, since the entire circularprofile moves uniformly at the vehicle speed, the displacement of airfrom around the moving circular profile is generally uniformlydistributed with elevation across the forwardly facing vertical profileof the wheel. Thus, these pressure drag forces (P, as shown in FIG. 24and FIG. 25) are also generally evenly distributed with elevation acrossthe entire forwardly facing vertical profile of the wheel, and centerednear the axle. And these evenly distributed pressure drag forces arisegenerally in proportion only to the effective headwind speed of thevehicle.

Frictional drag forces (F, as shown FIG. 25), however, are concentratednear the top of the wheel where moving surfaces generally exceed vehiclespeed—while the lower wheel surfaces move at less than the vehiclespeed. Since drag forces are generally proportional to the square of theeffective wind speed, it becomes apparent that with increasing windspeed, that these upper wheel frictional drag forces directed upon themoving surfaces increase much more rapidly than do pressure drag forcesdirected upon the forward profile of the wheel. Indeed, these frictiondrag forces generally arise in much greater proportion to an increasingeffective headwind speed of the vehicle. Nevertheless, these increasedfrictional drag forces being directed on the upper wheel is only apartial factor contributing to augmented wheel drag forces beingresponsible for significantly retarded vehicle motion.

Significantly, both types of drag forces can be shown to exert momentsof force pivoting about the point of ground contact. And as such, eithertype of drag force exerted upon the upper wheel retards vehicle motionconsiderably more than a similar force exerted upon a substantiallylower surface of the wheel. Minimizing these upper wheel drag forces istherefore critical to improving propulsive efficiency of the vehicle.

Also important—and due to the rotating geometry of the wheel—it can beshown that the vehicle propulsive force on the wheel appliedhorizontally at the axle must substantially exceed the net opposing dragforce exerted near the top of the wheel. These forces on a wheel areactually leveraged against each other, both pivoting about the samepoint—the point on the wheel which is in stationary contact with theground—and which is constantly changing lateral position with wheelrotation. Indeed, with the geometry of a rolling wheel momentarilypivoting about the stationary point of ground contact, the lateral dragand propulsive forces each exert opposing moments of force on the wheelcentered about this same point in contact with the ground.

Furthermore, unless the wheel is accelerating, the net torque from thesecombined moments on the wheel must be null: The propulsive momentgenerated on the wheel from the applied force at the axle mustsubstantially equal the opposing moment from drag forces centered nearthe top of the wheel (absent other resistive forces, such as bearingfriction, etc.). And the propulsive moment generated from the appliedforce at the axle has a much shorter moment arm (equal to the wheelradius) than the opposing moment from the net drag force centered nearthe top of the wheel (with a moment arm substantially exceeding thewheel radius)—since both moment arms are pivoting about the samestationary ground contact point. Thus, for these opposing moments toprecisely counterbalance each other, the propulsive force applied at theaxle—with the shorter moment arm—must substantially exceed the net dragforce near the top of the wheel.

In this way, the horizontal drag forces exerted upon the upper surfacesof the wheel are leveraged against opposing and substantially magnifiedforces at the axle. Hence, a relatively small frictional drag forcecentered near the top of the wheel can have a relatively high impact onthe propulsive counterforce required at the axle. Shielding these upperwheel surfaces can divert much of these headwind-induced drag forcesdirectly onto the vehicle body, thereby negating much of the retardingforce amplification effects due to the pivoting wheel geometry.

Moreover, since the propulsive force applied at the axle exceeds thecombined upper wheel drag forces, a lateral reaction force (R, as shownin FIG. 25) upon the wheel is necessarily developed at the groundcontact point, countering the combined unbalanced propulsive and dragforces on the wheel: Unless the wheel is accelerating, the reactionforce at the ground, together with the upper wheel net drag forces(F+P), combine (A=F+R+P, as shown in FIG. 25) to countervail the lateralpropulsive force (A) applied at the axle. This reaction force istransmitted to the wheel through frictional contact with the ground. Inthis way, an upper wheel drag force is further magnified against theaxle. For these multiple reasons, it becomes crucial to shield the upperwheel surfaces from exposure to headwinds.

Given that the propulsive force (A) applied at the axle must overcomeboth the net wheel drag forces (F+P) and the countervailing lowerreaction force (R) transmitted through the ground contact point, it canbe shown that the net drag force upon the upper wheel can oppose vehiclemotion with nearly twice the sensitivity as an equivalent drag forceupon the static frame of the vehicle. Hence, shifting the impact ofupper wheel drag forces to the static frame can significantly improvethe propulsive efficiency of the vehicle.

Furthermore, as drag forces generally increase in proportion to thesquare of the effective wind speed, the more highly sensitive upperwheel drag forces increase far more rapidly with increasing headwindspeeds than do vehicle frame drag forces. Thus, as the vehicle speedincreases, upper wheel drag forces rapidly become an increasingcomponent of the total drag forces retarding vehicle motion.

And given the greater sensitivity of speed-dependent upper wheel dragforces—as compared against vehicle frame drag forces—to the retarding ofvehicle motion, considerable effort should first be given to minimizingupper wheel drag forces. And shielding the faster-moving uppermostsurfaces of the wheel assembly from oncoming headwinds, by using thesmallest effective fairing assembly, is an effective means to minimizeupper wheel drag forces.

Contrarily, drag forces on the lower wheel generally oppose vehiclemotion with reduced sensitivity compared to equivalent drag forces onthe static frame of the vehicle. Propulsive forces applied at the axleare levered against lower wheel drag forces, magnifying their impactagainst these lower wheel forces. Shielding lower wheel surfaces cangenerally negate this mechanical advantage, and can actually increaseoverall drag on the vehicle.

Moreover, as discussed above, headwinds on the static frame generallyexceed the speed of winds impinging the lower surfaces of the wheel.Hence, frictional drag forces on the lower wheel surfaces are greatlyreduced. Thus, it is generally counterproductive to shield the wheelbelow the level of the axle. Drag on a vehicle is generally minimizedwith upper wheel surfaces shielded from headwinds and with lower wheelsurfaces exposed to headwinds.

Wheel drag sensitivity to retarding vehicle motion becomes even moresignificant in the presence of external headwinds. With externalheadwinds, the effective wind speed impinging the critical upper wheelsurfaces can well exceed twice the vehicle speed. Shielding protects theupper wheel surfaces both from external headwinds, and from headwindsdue solely to vehicle motion.

Indeed, wheel surfaces covered by the shield are exposed to winds duesolely to wheel rotation; headwinds are deflected. The effective dragwinds beneath the shield are generally directed tangentially to rotatingwheel surfaces, and vary in proportion to radial distance from the axle,reaching a maximum speed at the wheel rim equal to the vehicle speed,regardless of external headwinds. Since drag forces vary generally inproportion to the square of the wind speed, the frictional drag forcesare considerably reduced on shielded upper wheel surfaces. Using thesewind shields, shielded wheel surfaces are exposed to substantiallyreduced effective wind speeds—and to generally much less than half ofthe drag forces without shielding.

Diminished drag forces from external headwinds impinging the slowermoving lower surfaces of a rolling wheel generally oppose wheel motionwith much less retarding torque than drag forces from winds impingingthe faster upper surfaces. Indeed, tests demonstrate that with uppershields installed on a suspended bicycle wheel, the wheel will spinnaturally in the forward direction when exposed to headwinds. Withoutthe shields installed, the same wheel remains stationary when exposed toheadwinds, regardless of the speed of the headwind. And an unshieldedspinning wheel will tend to stop spinning when suddenly exposed to aheadwind. This simple test offers an explanation for the unexpectedresult achieved from Greenwell—mentioned above—and demonstrates that byminimally shielding only the upper wheel surfaces from externalheadwinds, the overall drag upon the rotating wheel can be substantiallyreduced.

Furthermore, as external headwinds upon a forwardly rotating vehiclewheel add relatively little frictional drag to the lower wheelsurfaces—which move forward at less than the vehicle speed—but add farmore significant drag to the upper wheel surfaces, which move forwardfaster than the vehicle speed and which can more significantly retardvehicle motion, shielding the upper wheel surfaces against headwinds isparticularly beneficial. Since drag forces upon the wheel are generallyproportional to the square of the effective wind speed thereon, and theadditional drag on the wheel—and thereby on the vehicle—increasesrapidly with headwinds, shielding these upper surfaces greatly reducesthe power required to propel the vehicle. Moreover, the relativeeffectiveness of shielding upper wheel surfaces generally increases withincreasing headwinds.

An examination of the retarding wind vectors on a rotating wheel canreveal the large magnitude of drag retarding moments upon the uppermostwheel surfaces, relative to the lower wheel surfaces. And an estimate ofthe frictional drag torque on the wheel can be determined by firstcalculating the average moments due to drag force vectors at variouspoints—all pivoting about the ground contact point—on the wheel (resultsshown plotted in FIG. 17), and then summing these moments at variouswheel elevations above the ground and plotting the results (FIG. 18).The area under the resulting curve (shown in FIG. 18 as a series ofcurves representing various headwind conditions) then represents thetotal frictional drag (absent profile drag) torque upon the wheel.

In order to determine the relationship between this torque and elevationon the wheel, the magnitudes of the drag wind vectors that areorthogonal to their corresponding moment arms pivoting about the pointof ground contact must first be determined. These orthogonal vectorcomponents can be squared and then multiplied by the length of theircorresponding moment arms, in order to determine the relative momentsdue to drag at various points along the wheel rim.

The orthogonal components of these wind vectors tend to increaselinearly with elevation for points on the rim of the wheel, and also forpoints along the vertical mid-line of the wheel. Calculating the momentsalong the vertical mid-line of the wheel can yield the minimum relativedrag moments at each elevation. Calculating an average of the maximumdrag moment at the rim combined with the minimum drag moment along themid-line can then yield the approximate average drag moment exerted ateach elevation upon the wheel. Multiplying this average drag moment bythe horizontal rim-to-rim chord length can yield an estimate of the dragtorque exerted upon the wheel at each elevation level (FIG. 18). Thesecalculations are simply determined from the geometry of the rotatingwheel; the object of this analysis is to determine the likely relativemagnitudes of drag torques upon the wheel at various elevations.

From the resulting plots (FIG. 18), it can be estimated that theuppermost approximate one-third section of the wheel likely contributesmost of the overall drag torque upon the wheel. Thus, by shielding thisupper section from headwinds, drag torque can be considerably reduced.With upper-wheel shielding, as noted above, the relative winds beneaththe shield are due mostly to wheel rotation, and are generally directedtangentially to the wheel. The resulting drag torque under the shieldedsections can then be determined as above, and compared with theunshielded drag torque for similar headwind conditions.

These calculations—generally confirmed by tests—indicate a substantialreduction in retarding drag torque upon the shielded upper wheelsurfaces. In the absence of external headwinds, the plots of FIG. 18indicate that shielding the uppermost approximate one-third section ofthe wheel can reduce the drag torque of this section considerably, by asmuch as 75 percent. Moreover, repeating calculations and testing with anexternal headwind equal to the vehicle speed indicates that upper wheelshielding can reduce the comparative upper wheel drag torque of thissection by still more, perhaps by as much as 90 percent. Hence, thepotential effectiveness of shielding upper wheel surfaces can besignificant, especially with surfaces having higher drag sensitivities,such as wheel spoke surfaces.

As discussed above, since upper wheel drag forces are leveraged againstthe axle—thereby magnifying the propulsive counterforce required at theaxle—an increase in drag force on the wheels generally retards vehiclemotion much more rapidly than does an increase in other vehicle dragforces. And while under external headwind conditions, the total drag ona vehicle with wheels exposed directly to headwinds increases still morerapidly with increasing vehicle speed.

Shielding upper wheel surfaces effectively lowers the elevation of thepoint on the wheel where the effective net drag force is exerted,thereby diminishing the magnifying effect of the propulsive counterforcerequired at the axle, as discussed above. As a result, the reduction indrag force upon the vehicle achieved by shielding the upper wheelsurfaces is comparatively even more significant with increasing externalheadwinds. Shielding these upper wheel surfaces can thereby improverelative vehicle propulsion efficiency under headwinds by an evengreater margin than under null wind conditions.

Moreover, shielding these upper wheel surfaces can be particularlybeneficial to spoked wheels, as round spokes can have drag sensitivitiesmany times greater than that of more streamlined surfaces. As roundspokes—in some configurations—can have drag coefficients ranging fromone to two orders of magnitude greater than corresponding smooth,streamlined surfaces, shielding the spokes of the upper wheel fromexternal wind becomes particularly crucial in reducing overall drag uponthe wheel.

Accordingly—given these multiple factors—a relatively small streamlinedfairing attached to the vehicle structure and oriented to shield theupper surfaces of the wheel assembly from oncoming headwindssubstantially reduces drag upon the wheel, while minimizing total dragupon the vehicle. Consequently, an embodiment includes the addition ofsuch a fairing to any wheeled vehicle—including vehicles having spokedwheels, where the potential drag reduction can be even more significant.

The addition of such minimal fairings to each side of a traditionalspoked bicycle wheel, for example, reduces windage losses and improvespropulsive efficiency of the bicycle, particularly at higher cyclespeeds or in the presence of headwinds, while minimizing cycleinstability due to crosswind forces. Since crosswinds are a significantfactor restricting the use of larger wheel covers, minimizing thefairing size is also an important design consideration. And minimizingform drag induced by the forward-facing profile of the fairing also willinfluence the fairing design. The preferred fairing size will likelysubstantially cover the upper section of the exposed wheel, and beplaced closely adjacent to the wheel surfaces, consistent with generaluse in bicycles. In heavier or powered cycles, design considerations maypermit somewhat larger fairings, covering even more of the wheelsurfaces.

As shielding upper wheel surfaces can reduce overall drag on thevehicle, while simultaneously augmenting the total frontal profile areaof the vehicle exposed to headwinds, a natural design constraint emergesfrom these competing factors: Shields should be designed sufficientlystreamlined and positioned sufficiently close to wheel surfaces toprovide reduced overall vehicle drag. And as shielding effectivenesspotentially increases under headwind conditions, shields designed withlarger surface areas and larger frontal profiles may still providereduced overall vehicle drag under headwind conditions, if not undernull wind conditions. Thus, a range of design criteria may be applied toselecting the best configuration and arrangement of the fairing, andwill likely depend on the particular application. In any particularapplication, however, the embodiment will include a combination ofdesign factors discussed above that will provide a reduction in overallvehicle drag.

In a cycle application, for example, fairings positioned within thewidth of the fork assembly will likely provide the most streamlineddesign which both shields spokes from headwinds but also minimizes anyadditional form drag profile area to the vehicle frame assembly. Inother applications, insufficient clearances may preclude positioning thefairings immediately adjacent to moving wheel surfaces. In suchsituations, headwinds may be sufficient in magnitude to cause areduction in overall vehicle drag to justify the use of wider upperwheel fairings—positioned largely outside the width of the forkassembly—with extended forward profile areas.

Furthermore, from the previous analysis a consideration the drag torquecurves wholly above the level of the axle, it becomes apparent thatshielding the wheel is best centered about an elevation likely between75 and 80 percent of the diameter of the wheel, or near the center ofthe area under the unshielded torque curve shown in FIG. 18. While dragforces are generally greatest in magnitude near the top of the wheel,the effective exposed topmost surface areas are much smaller, therebylimiting the magnitude of drag torques upon the uppermost surfaces ofthe wheel. Thus, the upper wheel fairing would best extend above andbelow this critical level (generally, between 75 and 80 percent of thediameter of the wheel) in order to optimally minimize drag upon thewheel. And as the surfaces forward of the axle are the first to beimpacted by headwinds, shielding these surfaces is essential todeflecting headwinds from the rearward surfaces. Thus, thehigher-sensitivity drag-inducing surfaces in the forward upper quadrantand centered about this critical elevation on the wheel generally needto be shielded for optimal minimization of drag. Thesehigher-sensitivity drag-inducing surfaces generally centered about thiscritical elevation and extending to include those surfaces with higherdrag-inducing sensitivities that are positioned mostly in the forwardupper quadrant of the wheel, but likely also to include much of thewheel surfaces positioned in the rearward upper quadrant, are hereindefined and later referred to as: major upper drag-inducing surfaces.And the critical level about which the major drag-inducing surfaces aregenerally centered in elevation is herein defined and later referred toas: critical elevation.

As discussed, the precise elevation about which the major upperdrag-inducing surfaces are centered, as well as the precise extent towhich surfaces in the forward quadrant and in the upper half of thewheel central structure are included in the major upper drag-inducingsurfaces, will depend on the particular application and operatingconditions. Certain wheel surfaces with higher drag sensitivities, suchas wheel spokes, generally need to be shielded when positioned withinthe region of the major upper drag-inducing surfaces. Other surfacessuch as smooth tire surfaces having lower drag sensitivities may alsobenefit from shielding if their surface areas are extensive, arepositioned near the critical level in elevation, or are the primaryupper wheel surfaces exposed to headwinds. In the example analysis ofFIGS. 17 and 18, a uniform surface across the wheel having a constantdrag-sensitivity was assumed. In any particular application, the uniquecombination of different wheel surfaces with differing dragsensitivities will determine the particular height of the criticalelevation level about which the major upper drag-inducing surfaces arecentered.

A similar analysis can be performed for form drag forces on the movingforward vertical profiles of the wheel rim or tire. The results obtainedare generally similar in form, though may differ somewhat in magnitudesas the effective wind speeds on the moving profiles are generally loweron the upper wheel—equal to the vehicle speed—and will depend on theparticular application, including the total area of the wheel forwardprofile exposed to headwinds, and to headwind and vehicle speeds.Nevertheless, the net pressure drag torque caused by the moving outlineof the wheel is also centered above the level of the axle, and therebymerits consideration in determining the particular height of thecritical elevation level, and in the ultimate configuration of thefairing.

Hence, the fairing shown in FIG. 1 is best configured to shield theuppermost and forward wheel surfaces, and to extend rearward to at leastpartially shield the forward profile of the trailing portion of theupper wheel rim, consistent with the further requirement to extenddownward as much as practical to the level of the axle. As mentioned,crosswind considerations will also influence the ultimate configurationfor a particular application.

In consideration of further embodiments described below, the operatingprinciples described above will generally apply, and may be referredthereto.

Second Embodiment—Description—FIG. 2

As shown in FIG. 2, a streamlined fender 7 is attached to the inside ofthe front-fork tube assembly 2 of a typical cycle having spoked wheels 4with studded tires 8. The fender 7 is positioned closely adjacent totire 8, covering the approximate upper and front-most quadrant of thetire 8, and is rigidly fixed to the stationary portion of axle assembly9 using struts 10. The fender 7 has sufficient structural rigidity toallow close placement to tire 8, thereby minimizing any oncomingheadwinds from leaking between tire 8 and fender 7.

With fender 7 configured in this way, the treads near the top of thetire 8 are shielded from headwinds. Shielded this way, the topmostsurfaces of tire 8 are moving at an effective wind speed closer to theground speed of the cycle, rather than moving with respect to theoncoming external wind at an effective speed of up to nearly twice theground speed of the cycle. As a result, the aerodynamic drag forcesexerted upon the upper treads of tire 8 are substantially reduced.

The reduction drag force has the greatest effect near the top of tire 8,where the surfaces of tire 8 are moving fastest with respect to externalwinds otherwise impinging thereupon. As the uppermost surfaces of tire 8rotate away from the topmost point to an intermediate position withrespect to either of two lateral midpoints on the tire 8, these dragforces are greatly reduced. Thus, the embodiment shown in FIG. 2 coversthis critical uppermost and forward-oriented quadrant of tire 8,minimizing the addition of unnecessary weight and drag-inducingstructure to the cycle.

Second Embodiment—Operation—FIG. 2

An embodiment including a forwardly oriented fender 7, shielding theuppermost outer surfaces of the tire 8 from oncoming headwinds, canoffer not only similar aerodynamic benefits to fairing 1 of FIG. 1 inreducing frictional drag forces on tire surfaces, but can alsosubstantially reduce form drag forces on the wheel's forwardly facingprofiles.

As discussed above, both frictional and pressure drag forces can beshown to exert moments of force pivoting about the point of groundcontact. And these forces are magnified against the propulsive forcerequired at the axle. And as such, either type of drag force exertedupon the upper wheel retards vehicle motion considerably more than asimilar force exerted either upon a lower surface of the wheel, ordirectly upon the frame or body of the vehicle. Minimizing these upperwheel drag forces is therefore critical to improving propulsiveefficiency of the vehicle. Fender 7 is an effective means to minimizeboth frictional drag forces on upper wheel surfaces, and pressure dragforces exerted on the upper wheel. Fender 7 shields tire 8 fromheadwinds and thereby reduces drag on surfaces of tire 8. Fender 7 alsodeflects headwinds from tire 8 and thereby shifts headwind form dragforces normally directed upon the upper wheel forward profile to beinstead directed upon the vehicle frame. Thus, fender 7 reduces wheelform drag force (as well as tire frictional drag force) magnificationeffects significantly.

And similar to the first embodiment of FIG. 1, the optimum design for aparticular headwind application will size fender 7 sufficientlyextensive in frontal profile area to effectively shield tire 8 fromheadwinds, but sufficiently narrow to minimize any added form drag tothe vehicle, and which will result in an overall reduction in vehicledrag. For certain wheels having tires with rough, high-drag sensitivitytread patterns, such a topmost and forwardly-oriented fender 7 canprovide sufficient reduction in total upper tire drag to offset anyadded vehicle drag from the fender itself. In higher speed vehicles,particularly those having wider tires exposed directly to headwinds—suchas certain jeep-type automobiles or trucks—using an upper andforwardly-oriented fender 7 to shield the upper wheel surfaces may offerdramatic reductions in vehicle drag.

Third Embodiment—FIG. 3

Similarly, as shown in FIG. 3, a streamlined combination fender andfairing assembly 12 is attached to the inside of front fork tubeassembly 2 of a typical cycle having spoked wheels 4. The fender portionof the combination assembly 12 is positioned closely adjacent to thetire 8 covering the approximate upper and front-most quadrant of thetire 8. The fairing portions of the combination assembly 12 arepositioned closely adjacent to the inner wheel structure of wheel 4covering the approximate upper and front-most quadrant on each side ofwheel 4. The combination assembly 12 is provided sufficient structuralrigidity to allow close placement to wheel 4 and tire 8, therebyminimizing any oncoming headwinds from leaking either between tire 8 andthe fender portion of the combination assembly 12, or between the innerstructure of wheel 4 and the fairing portions of the combinationassembly 12.

With the combination fender and fairing assembly 12 configured in thisway, both the spokes 5 and the treads of tire 8 near the top of thewheel 4 are shielded from headwinds. And similar to the embodiments ofFIG. 1 and FIG. 2, the aerodynamic drag forces exerted upon the topmostspokes 5 and the upper treads of tire 8 are substantially reduced, andthereby may offer dramatic reductions in vehicle drag.

In addition, however, including fairing assembly 12 in this embodimentprovides an additional measure of profile shielding to the frontal areaof the trailing upper section of wheel 4, thereby further reducing totalwheel profile form drag. And similar to the second embodiment of FIG. 2,the optimum design for a particular headwind application will sizecombination fender and fairing assembly 12 sufficiently extensive inboth frontal profile area and fairing size to effectively shieldsurfaces of wheel 4 and tire 8 from headwinds, but sufficiently narrowand compact in size to minimize any added drag to the vehicle, and whichwill result in an overall reduction in vehicle drag.

Fourth Embodiment—FIG. 4

As shown in FIG. 4, a streamlined fender 7 is attached to a typicalsports car 13 having otherwise exposed tires 8. The fender 7 ispositioned closely adjacent to the tire 8, covering the approximateupper and front-most quadrant of tire 8. The fender 7 is attached eitherto the moving wheel suspension assembly of wheel 4, thereby minimizingany relative motion between the suspended wheel 4 and the fender 7, ordirectly to the body structure of car 13 with the wheel suspensiondisplacement range substantially constrained. The fender 7 is providedsufficient structural rigidity to allow close placement to tire 8,thereby minimizing any oncoming headwinds from leaking between tire 8and fender 7.

With fender 7 configured in this way, the tread near the top of tire 8is shielded from headwinds. And similar to the embodiment of FIG. 2, theaerodynamic drag forces exerted upon the upper surfaces of tire 8 aresubstantially reduced, and thereby may offer dramatic reductions invehicle drag.

Fifth Embodiment—FIG. 5

As shown in FIG. 5, a streamlined combination fender and fairingassembly 12 is attached to a typical sports car 13 having otherwiseexposed tires 8 and spoked wheels 4. The fender portion of thecombination assembly 12 is positioned closely adjacent to the tire 8covering the approximate upper and front-most quadrant of the tire 8.The combination assembly 12 is attached either to the moving wheelsuspension assembly of wheel 4, thereby minimizing any relative motionbetween suspended wheel 4 and combination assembly 12, or directly tothe body structure of car 13 with the wheel suspension displacementrange substantially constrained. The fairing portions of combinationassembly 12 are positioned closely adjacent to the inner wheel structureof wheel 4 covering the approximate upper and front-most quadrant oneach side of wheel 4. The combination assembly 12 is provided structuralrigidity sufficient to allow close placement to wheel 4 and tire 8,thereby minimizing any oncoming headwinds from leaking either betweentire 8 and the fender portion of combination assembly 12, or between theinner structure of wheel 4 and the fairing portions of combinationassembly 12.

With the combination fender and fairing assembly 12 configured in thisway, both the spokes 5 and the treads of tire 8 near the top of thewheel 4 are shielded from headwinds. And similar to the embodiment ofFIG. 3, the aerodynamic drag forces exerted upon the upper spokes 5 andthe upper surfaces of tire 8 are substantially reduced, and thereby mayoffer dramatic reductions in vehicle drag.

Sixth Embodiment—Description—FIG. 6

As shown in FIG. 6, a streamlined wind-deflecting fairing 14 is shownattached to a typical sports car 13 having otherwise exposed tires 8.The wind-deflecting fairing 14 is positioned slightly forward andclosely adjacent to the tire 8, shielding the approximate upperfront-most quadrant of tire 8 from headwinds. The wind-deflectingfairing 14 is attached either to the moving wheel suspension assembly ofwheel 4, thereby minimizing any relative motion between the suspendedwheel 4—and tire 8—and wing fairing 14, or directly to the bodystructure of car 13 with the wheel suspension displacement rangesubstantially constrained. The wind-deflecting fairing 14 is designedwith minimal surface area, but with sufficient area to deflect headwindfrom otherwise impinging upon the upper surfaces of tire 8.

With wind-deflecting fairing 14 configured in this way, the tread nearthe top of tire 8 is shielded from headwinds. And similar to theembodiments of FIGS. 2, 3, 4 and 5, the aerodynamic drag forces exertedupon the upper surfaces of tire 8 are substantially reduced, and therebymay offer dramatic reductions in vehicle drag.

Sixth Embodiment Operation—FIGS. 6 and 25

As indicated above, a countervailing ground reaction-force (R, as shownin FIG. 25) opposing vehicle forward motion is naturally developed uponthe wheel, primarily in response to the upper-wheel drag forces. Thisreaction force is transmitted to the wheel through frictional groundcontact with the tire. As the net drag force grows generally with thesquare of the average effective wind speed upon the wheel, thesefrictional ground contact forces increase in similar proportion.

As a result, proportional down-forces must somehow be developed upon thewheel in order to maintain firm contact with the ground, preventing tireskidding and loss of vehicle control. These down-forces are generallydeveloped using drag-inducing wings and body moldings on the vehicle,often greatly reducing the propulsive efficiency of the vehicle.

Introducing wind-shielding fairings to the upper wheel areas can reduceboth the drag forces acting thereon, and the drag inducing down-forcesneeded to maintain firm ground contact. And the use of a minimalwind-deflecting fairing that also provides a measure of down-force canbe particularly beneficial in high-speed vehicle applications. Thus, theuse of minimal wind-deflecting upper wheel fairings can further improveboth the propulsive efficiency and directional stability of manyhigher-speed vehicles.

Seventh Embodiment—Description—FIG. 7

In FIG. 7, a streamlined fairing 1 is shown as in FIG. 1, but includesan adjustable fairing section 15 pivoting at attachment point 16,whereby the total effective area of the combined fairingassembly—shielding the wind from wheel surfaces—can be adjusted toaccommodate different crosswind conditions.

Seventh Embodiment—Operation—FIG. 7

A further embodiment may include adjustable means for varying theexposed surface area of the fairing 1, thereby providing adjustment tothe effective shielding of the wheel 4 from oncoming headwinds. Such afairing mounted on a bicycle, for example, could be collapsed under highcrosswind conditions for minimal exposed area, covering only the verytopmost surfaces of the wheel, and thereby minimizing potentialcrosswind forces directed upon the wheel. Under normal wind conditions,the fairing could be extended, covering more of the critical upper-wheelsurfaces, thereby maximizing propulsive efficiency.

Adjustable fairing means could also include streamlined holes or slotsin the fairing, arranged for minimal drag, but otherwise enabling somecrosswinds to penetrate the fairing. While some loss in potentialreduction in drag may result from utilizing such perforated means in thefairing, under higher crosswind conditions this configuration may becomedesirable.

Finally, and particularly for higher speed applications, automatic meansfor adjustment of the fairing area could be provided to automaticallyoptimize the exposed fairing area for changing operating conditions.

Eighth Embodiment—Description—FIGS. 8, 9, 10, 11, 12 and 13

In FIGS. 8 and 9, several examples of prior-art wheels typically foundon high-performance automobiles are shown, having outwardly orientedsquare-profile spokes, which are generally exposed to headwinds. Thesquare cross-sectional profile of prior art spokes is shown in FIG. 10.The streamlined cross-sectional oval profile of the embodiment spokes isshown in FIG. 11. FIG. 12 shows an example of a wheel with generallyoval cross-sectional spokes. FIG. 13 shows an example of a wheel withgenerally oval cross-sectional spokes where the spokes are shown in tworows, one row being offset more toward the inside of the wheel, therebyincreasing the strength of the wheel in the axial direction.

Eighth Embodiment—Operation—FIGS. 8, 9, 10, 11, 12, 13 and 33

Square spokes have higher sensitivity to drag than either round or morestreamlined oval-shaped spokes. Given the importance—establishedabove—of reducing the drag on rotating wheel surfaces over that on othervehicle surfaces, it becomes evident that considerable effort should begiven to reducing spoke drag on high-speed wheels.

Thus, an embodiment includes the use of tapered, generally oval-shapedspokes on automotive wheels, especially on wheels with spokes directlyexposed to headwinds. For example, the use of an oval-profiled spokewith a two-to-one dimensional ratio may reduce drag by a factor of twoor more, over a similar square-profile spoke. And further streamliningthe spoke can reduce drag sensitivity even more.

As axial forces upon the wheel are transmitted more efficiently withspokes having square profiles than with streamlined spokes, streamlineddesigns for automotive spokes may have been largely overlooked.Streamlined oval profiled spokes can provide sufficient axial strengthby offsetting the streamlined spokes in the axial direction within thewheel as shown in FIG. 13, and by providing a nonparallel arrangementbetween the offset rows of spokes as shown in FIG. 33. Using arelatively thin streamlined spoke, in nonparallel arrangement with othersimilar spokes offset axially (and likely circumferentially) within thewheel, adequate axial structural rigidity can be obtained.

The reduced drag sensitivity of the streamlined spoke used in high-speedautomotive wheels can significantly improve vehicle performance—reducingfuel consumption—and traction, especially at higher vehicle speeds andunder headwind conditions.

Ninth Embodiment—Description—FIGS. 14, 15 and 16

In FIG. 14, a streamlined spoke tailfin 20 is installed over a roundwire spoke 21—shown in cross-section A-A of FIG. 15—typically used on acycle. Pivoting rings 22 affixed to tailfin 20 enable tailfin 20 toswivel about the spoke 21, and thereby permitting tailfin 20 toautomatically adjust its orientation in response to varying crosswinds.In FIG. 15, the wider profile of the spoke tailfin 20 is shown rotatablyattached to spoke 21. In FIG. 16, several spoke tailfin covers 23 ofdifferent sizes—shown in the configuration of a cover but similar instreamlined profile to tailfin 20 shown in FIG. 14—are shown installedon a spoke 21. The tailfin cover 23 includes a through-hole containingspoke 21 within its length, enabling the tailfin cover 23 to swivelabout spoke 21, and thereby permitting tailfin cover 23 to automaticallyadjust its orientation in response to varying crosswinds.

Ninth Embodiment—Operation—FIGS. 14, 15 and 16

The streamlined profile of the swiveling spoke tailfin may offer greatlyreduced drag over round spokes, without the potential increase in dragsensitivity of bladed spokes exposed to crosswinds. Use of thestreamlined spoke tailfin may reduce drag sensitivity of the round spokeconsiderably, in some instances by up to a factor of 10.

Eliminating crosswind turbulence upon the streamlined profile isessential to minimize drag on the spokes under crosswind conditions. Therelative crosswind-to-headwind vector directed on a point on the wheelvaries significantly with wheel rotation. Near the top of the wheel,headwinds are strongest, and any relative crosswinds are lesssignificant. Near the bottom of the wheel, headwinds are minimized andcrosswinds are thereby more significant relative sources of drag on thewheel surfaces. Allowing the spoke tailfin to swivel enables the tailfinto adjust to immediate relative crosswinds, which can vary continuallywith the rotation of the wheel.

The spoke tailfin can be designed either to extend the entire length ofthe spoke, or to extend over only a portion of the spoke, such as overthe outermost section of the spoke nearest the rim, which moves fastestnear the top of the wheel, and is thereby exposed to the fastestheadwinds.

Alternatively, the spoke tails may be divided in several independentsections along the length of the spoke, allowing independent adjustmentto the varying crosswind components along the radial direction of thewheel. And these tailfin sections can be different in both size andconfiguration, to best minimize drag, as shown in FIG. 16. For example,tailfin sections nearest the rim—at the top in FIG. 16—are exposed tothe faster headwinds and may be designed for more extensivestreamlining, while sections closer to the hub—at the bottom in FIG.16—being exposed to slower headwinds and greater relative crosswindvector components, may be designed more compactly for more rapidre-orientation. Or the tailfin could be configured with a taperedcross-sectional profile similar in form to the tapered spoke embodiment,described below and referenced in FIGS. 19, 20, 21, 22 and 23, whichvaries along its entire length.

While shielding the spokes with a fairing is an effective means ofreducing drag due to headwinds, drag induced solely from winds due towheel rotation remains largely unaffected. Indeed, the spokes on thelower half of the wheel are relatively less affected by headwinds, andare more affected by the vector components of wind due to wheelrotation. Using streamlined spoke tailfins, drag on the lower spokes canalso be reduced. Moreover, swiveling spoke tailfin covers used inconjunction with upper wheel fairings can offer significant reduction inoverall drag upon the wheel—and thereby on the vehicle—while minimizingsensitivity to crosswinds.

Tenth Embodiment—Description—FIGS. 19, 20, 21 22 and 23

In FIGS. 19 and 20, a streamlined spoke for use in racing-style bicyclewheels, tapers in the broader width from the wheel rim to the wheel hub.In FIG. 21, the profile—shown in cross-section—of the more streamlinedend of the spoke is shown. The spoke profile varies along the length ofthe spoke—from rim to hub—with the more thin and streamlined partnearest the rim and the more circular part nearest the hub. In FIG. 22,the profile—shown in cross-section—of the middle of the spoke is shown.In FIG. 23, the profile—shown in cross-section—of the end of the spokenearest the wheel hub is shown.

The profile is shaped to maintain a generally constant total area incross-section, in order to retain a relatively constant tensile strengthalong the full length of the spoke. The spoke profile may includecross-sectional areas varying somewhat along the spoke length, typicallywith larger areas nearest the ends of the spoke to enhance strength nearattachment points. Nearest the wheel rim, the streamlined profile ismore elliptical (or flat like a blade or thin wing), as shown in FIG.21, while nearest the hub the profile becomes more closely circular—asshown in FIG. 23. While the general trend for tapering the spoke is asshown, the particular application will determine just how thin and widethe spoke is near the rim, and how more oval or circular the spokecross-sectional profile becomes near the hub.

Tenth Embodiment—Operation—FIGS. 19, 20, 21 22 and 23

Streamlined spokes reduce drag upon the wheel in the presence of directheadwinds. A crosswind directed upon the wheel can cause turbulenceacross the broad face of the streamlined spoke, quickly increasing dragthereon. Eliminating crosswind turbulence upon the streamlined profileis essential to minimizing drag under crosswind conditions. The designchallenge becomes to minimize drag through spoke streamlining over thewidest range of crosswind conditions; too wide a blade design canexacerbate drag under even minimal crosswinds, thereby negating anyadvantage of the streamlined spoke profile.

Notably, the relative crosswind-to-headwind vector component variessignificantly depending on the relative location on the wheel. Near thetop of the wheel, headwinds are strongest, and any relative crosswindsare less significant. Near the bottom of the wheel, headwinds areminimized and crosswinds are more significant. Thus, crosswinds can be amore significant relative source of drag on wheel surfaces closer to theground.

The broader width of the bladed spoke provides greater streamlining forthe higher speed headwinds near the top of the wheel, thereby minimizingdrag on these critical drag-inducing surfaces. Any turbulence from therelatively smaller crosswind components directed upon the faster movinguppermost portion of the bladed spokes is generally minimized. The samecrosswinds directed upon slower moving spoke surfaces near the center ofthe wheel are a more significant relative component of the total windvector thereon, and thus have a greater potential to induceturbulence—and thereby to increase drag.

And as lower surfaces of the wheel are exposed to substantially reducedheadwinds, and also contribute much less resistive torque upon thewheel, crosswind-induced turbulence on the lower spokes is a relativelyinsignificant factor contributing to overall vehicle drag when comparedto the upper wheel surfaces. Thus, spoke profiles are best tapered foroptimum reduced drag on upper wheel surfaces, rather than for lowerwheel surfaces.

As a circular spoke profile generally produces far less drag-inducingturbulence than a flat blade profile when obliquely facing the wind, theportion of the spoke most sensitive to crosswinds should be closer tocircular in profile, while the portion of the spoke less sensitive tocrosswinds should be closer to a streamlined wing shape in profile.Thus, a tapered spoke—whose profile gradually transitions from thin andstreamlined near the rim of the wheel, to more oval or circular near thecentral hub of the wheel—can reduce the drag on the spoke over a widerrange of crosswind conditions than traditional generally constantcross-sectional profile—either bladed or circular—spoke designs.

Eleventh Embodiment—FIGS. 26, 27, 28, 29 and 30

In FIG. 27, an aggressive tire tread block pattern is shown having treadblocks which taper smoothly in profile on the leeward side, therebyreducing drag. The tread blocks are spaced apart and arranged to permitair displaced by the tread to flow smoothly between, around and overeach block, minimizing any flow separation—and thereby turbulence—behindeach individual tread block. The relatively sharp, angular windward sideof each block thereby provides for aggressive traction for typicaloff-road vehicle applications. However, the smoother leeward side ofeach tread block provides substantial streamlining for upper wheel dragreduction.

Tires using these streamlined tread blocks are thereby typicallydesigned for unidirectional rotation, since using these tires in reverserotation may reduce traction. Forward-facing windward surfaces of thetread blocks are generally sharp and angular in shape, and are thusoptimized for maximum traction on slippery ground; while the leeward,rearward-facing surfaces of the tread blocks are streamlined in designin order to reduce drag on each block.

The tread blocks are spaced and arranged to provide sufficientclearances to allow generally minimally restricted air flowthere-between, such that air flowing near the top of the tire isdeflected substantially between the tread blocks, rather than mostlyover the top of the tire. Near the top of the wheel assembly within theforward quadrant, air flowing around one block is largely divertedbetween the blocks, with minimal diversion of air over the top surfaceof the block. And tread blocks are generally arranged to direct divertedair largely toward the leeward side of adjacent blocks. In this way, thepressure differential between the windward and leeward surfaces of treadblocks is further minimized, thereby reducing form drag on the treadblocks even more.

With tire tread blocks configured in this way, the tread near the top oftire is substantially streamlined for impinging headwinds. Form dragupon the tread blocks is thereby substantially reduced, both where windsmost directly impinge the windward tread block surfaces, and where thefastest moving tread blocks are located—near the top of tire. Asdiscussed above, these uppermost wheel surfaces are also the mostcritical drag-inducing surfaces retarding vehicle motion and increasingdown-forces needed to maintain tire traction at higher speeds. Thus, itbecomes crucial to minimize drag on these upper tire tread blocks. Andstreamlining tread patterns for this location on the wheel assembly isan effective means to improve propulsive efficiency of the vehicle,particularly at higher vehicle speeds.

Various configurations of tread patterns may incorporate streamlinedtread blocks for reducing upper wheel drag forces against the tire.Tread blocks may taper either in width, depth or length. Alternativetread block patterns may incorporate more or less streamlined taperedlengths, depending on the application; longer streamlined blocks mayreduce the total number of tread blocks available to cover the tire,enhancing drag reduction for higher speed applications at the expense ofsomewhat reduced tire traction. Contrarily, shorter streamlined blocksmay increase the total number of tread blocks available to cover thetire, enhancing tire traction for slower speed applications at theexpense of somewhat reduced drag reduction.

Windward tread block surfaces may also include somewhat obliquepatterned arrangements—as shown in FIG. 28—rather than a more parallelorientation to the wheel axle often used to maximize traction.Alternatively, both windward and leeward tread block surfaces mayinclude streamlined designs, with the blocks being more substantiallyoval in shape; the oval blocks can be shaped eithersymmetrically-similar from front to back such as in FIGS. 29 and 30, orthe windward side can be shaped to be more sharp and angular, with theleeward surface being more streamlined and extended in length. In eithercase, sufficient clearance between the tread blocks must be maintainedin order to enable substantial air flow there-between, and to enablepressure relief behind adjacent tread blocks, thereby minimizing formdrag on the blocks. And for each of these embodiments, tread blocks arearranged in an aerodynamically optimized pattern.

And similar to other embodiments, the aerodynamic drag forces exertedupon the upper surfaces of tire are substantially reduced. Thus, thisembodiment may offer dramatic reductions in vehicle drag, particularlyfor faster vehicles with aggressively treaded tires that are exposeddirectly to headwinds.

Twelfth Embodiment—Description—FIGS. 31 and 32

As shown in FIG. 32, a wind-deflecting exhaust pipe array 34 is shown onone side of a typical top-fuel dragster race car 30, where the exhaustpipes are directed laterally in a distributed fashion to divertheadwinds from directly impinging the upper surfaces of the rearmostexposed tire 36. The extreme velocity of the air emanating from theexhaust pipes is used to deflect the headwinds generally above theuppermost surfaces of the rear tire. Rather than aligning the pipes allin an aligned array 32 with pipes directed mostly upward butsubstantially toward the outside of the vehicle—as is commonly seen inthe racing art as shown in FIG. 31—the pipes in this embodiment arearranged to direct the exhaust upward, but spanning the entire width ofthe rear tire. Properly positioned for the particular application, theejected exhaust gases deflect substantial headwinds upward above therear tire 36.

With the wind-deflecting exhaust pipe array 34 configured in this way,the surfaces near the top of rear tire 36 are substantially shieldedfrom impinging headwinds. And similar to the embodiment of FIG. 6, theaerodynamic drag forces exerted upon the upper surfaces of rear tire 36are substantially reduced, and may thereby offer dramatic reductions inhigh speed vehicle drag forces.

Variations on this embodiment are easily envisioned, and could beemployed wide variety of more traditional sports cars, automobiles, andmotorcycles. For example, exhaust pipes could be directed to exit in theupper forward portion of the fender well, directing exhaust gasessideways out the front of the well, thereby helping to shield the upperwheel surfaces from headwinds.

Advantages

From the description above, a number of advantages of some embodimentsbecome evident:

-   (a) The addition of simple upper wheel fairings to a bicycle can    improve rider propulsive efficiency—especially in headwinds—without    compromising rider comfort, significantly increasing wheel expense    or decreasing wheel durability.-   (b) The addition of simple upper wheel fairings to an electric    bicycle powered by rechargeable batteries can improve motor    propulsive efficiency, especially in headwinds, extending the    effective range of such power-assisted bicycles.-   (c) The addition of simple upper wheel fairings to a motorcycle can    improve propulsive efficiency—especially in headwinds—yielding    greater fuel economy.-   (d) The addition of simple upper wheel fairings to certain    automobiles having otherwise exposed tires, such as jeep-type    vehicles with elevated suspensions, can improve propulsive    efficiency especially in headwinds—yielding greater fuel economy.-   (e) The addition of simple upper wheel fairings to certain truck and    trailer wheels having otherwise exposed tires can improve propulsive    efficiency—especially in headwinds—yielding greater fuel economy.-   (f) The addition of simple upper wheel fairings to a bicycle or    motorcycle can reduce the down-force needed to ensure cycle    stability—especially important when navigating curved roads under    wet conditions—thus also better sustaining cornering traction during    intermittent wind gusts, and thereby improving cyclist safety.-   (g) The addition of simple upper wheel fairings to certain    high-speed vehicles having otherwise exposed tires can reduce the    down-force needed to ensure vehicle stability. Reducing down-force    in turn reduces the need for drag-inducing wings. In addition,    reducing down-force results in reduced tire rolling resistance and    bearing friction. These factors thereby improve propulsive    efficiency—especially in headwinds—yielding greater fuel economy.-   (h) The use of streamlined spokes in automotive wheels—especially in    wheels used in certain high-speed vehicles having otherwise exposed    spokes—can reduce both drag on the upper wheel and consequently the    down-force needed to ensure vehicle stability, and thereby improve    propulsive efficiency and vehicle safety—especially in    headwinds—yielding greater fuel economy.-   (i) The use of axially offset streamlined spokes in automotive    wheels—especially in wheels used in certain high-speed vehicles    having otherwise exposed spokes—can reduce both drag on the upper    wheel and consequently the down-force needed to ensure vehicle    stability, while maintaining the axial strength of the wheel. This    in turn can improve propulsive efficiency and vehicle    safety—especially in headwinds—yielding greater fuel economy.-   (j) The use of streamlined spoke tailfins in cycle wheels—especially    in wheels having otherwise exposed spokes—can reduce both drag on    the upper wheel and consequently and the down-force needed to ensure    vehicle stability, and thereby improve propulsive efficiency and    cycle safety, especially in headwinds.-   (k) The use of variably-tapered spokes in cycle wheels, where the    spokes are tapered from a streamlined profile near the rim to more    oval or circular profile near the wheel hub can reduce both drag on    the upper wheel and consequently the down-force needed to ensure    cycle stability, and thereby improve propulsive efficiency and cycle    safety—especially in headwinds—over a wide range of crosswind    conditions.-   (l) The use of tires having streamlined tread blocks arranged in an    optimal aerodynamic pattern can reduce both drag on the upper wheel    and consequently the down-force needed to ensure vehicle stability,    and thereby improve propulsive efficiency and vehicle    safety—especially in headwinds—yielding greater fuel economy.-   (m) The use of vehicle engine exhaust pipes arranged in an optimal    pattern to direct exhaust gases to deflect headwinds from otherwise    impinging upper wheel surfaces can reduce both drag on the upper    wheel and consequently the down-force needed to ensure vehicle    stability, and thereby improve propulsive efficiency and vehicle    safety—especially in headwinds—yielding greater fuel economy.

Conclusions, Ramifications, And Scope

Exposed wheels can generate considerable drag forces on a movingvehicle. These forces are directed principally near the top of thewheel, rather than being more evenly distributed across the entireprofile of the wheel. Moreover, these upper-wheel drag forces arelevered against the axle, thereby magnifying the counterforce requiredto propel the vehicle. As a result, a reduction in drag upon the upperwheel generally enhances propulsive efficiency significantly more than acorresponding drag reduction on other parts of the vehicle.

With the net drag forces being offset and directed near the top of thewheel, nearly equivalent countervailing reaction forces—also opposingvehicle motion—are necessarily transmitted to the wheel at the ground.These reaction forces necessitate augmented down-forces to be applied inhigher speed vehicles, in order to maintain static frictional groundcontact and, thereby, vehicle traction and directional stability. Aswings and other means typically used to augment these down-forces insuch vehicles can add significant drag, it becomes evident thatsubstantial effort should be made to reduce the upper wheel drag forceson most high-speed vehicles.

Modern automobile wheels, particularly those designed for use withlow-profile tires typically found on expensive sports cars, ofteninclude narrow spoke sections connecting the hub and rim, which becomesignificant sources of drag. Recent automotive design innovation onsports cars has focused on reducing upper-body drag while simultaneouslyincreasing down-forces to maintain traction. However, the wheel spokestypically used remain configured with inefficient drag profiles, and areoften located on the outside of the wheel assembly, where they can bemore directly exposed to headwinds. These spokes often have generallyrectangular cross-sectional profiles, which present significantlyincreased sensitivity to drag forces upon the upper wheel, and therebyupon the vehicle.

An embodiment includes the use of aerodynamic profiles on the spokes ofautomotive wheels, designed to minimize drag. By shaping the spokes inan oval cross-sectional profile with a two-to-one dimensional ratio, forexample, the drag sensitivity can generally be reduced by a factor oftwo or three times over a corresponding square-profile spoke design.Further narrowing of the streamlined profile can reduce drag sensitivityof the spokes even more. Given the magnifying property of upper wheeldrag forces to increasing both the down-forces needed to maintainvehicle traction and the overall drag upon the vehicle, configuringexposed spokes for minimal drag can be particularly helpful to improvingvehicle propulsive efficiency, especially for the outermost spokes andfor wheel sections nearest the rim which are most exposed to headwinds.

Drag can be reduced on the narrow round spokes of bicycle wheels, bysimply adding a streamlined tailfin section to the leeward side of thespoke. By enabling the streamlined tailfin to swivel about the spoke inresponse to varying crosswinds, drag can be minimized over a variety ofcrosswind conditions over the full range of wheel rotation. And severaltailfins of varying configurations can be used in combination tooptimize drag on the spoke, in response to variable crosswinds along thelength of the spoke on the upper wheel.

Alternatively, drag can be reduced on the bladed spokes of bicyclewheels, by simply by tapering the blade of the spoke at the rim to amore round profile at the wheel hub. By tailoring the profile of thespoke to accommodate the range of crosswind components—which vary inmagnitude from the rim to the hub—drag can be minimized on the spokeover a variety of crosswind conditions. Moreover, the tailfin could alsobe adapted with a similar variable cross-sectional profile along itslength in order to minimize drag on the spoke under crosswindconditions.

Furthermore, wider tires with aggressive tread patterns, designed formaximizing traction rather than minimizing drag, contribute tosignificant drag in many off-road type vehicles. Such tires often havetread patterns with rectangular profiles, which thus suffer highersensitivities to drag. These tires can be designed with more aerodynamictread patterns, with the tread blocks shaped either more in an ovalshape than a square or rectangular, or more tapered and streamlined onthe leeward sides, thereby maintaining much of the traction of therectangular profile tread tire. Furthermore, designing the gaps betweenthe tread blocks for streamlined flow of headwinds around these treadblocks, could improve vehicle propulsive efficiencies. Moreover, thetread blocks could be shaped to freely divert some of the headwind tothe side of the tire, especially for the upper forward profile sectionof the tire, rather than simply forcing the air up and over the tire,producing additional turbulence and more drag.

And as has been shown, the addition of minimal upper- andforwardly-oriented fairing and fender assemblies can substantiallyreduce total drag on the wheel, thereby enhancing the propulsiveefficiency of the vehicle. Such shielding devices should see widespreadapplication on a range of different vehicles, from human-poweredbicycles to high-speed motorcycles, automobiles, and trucks andtrailers. The embodiments shown are poised to contribute not only toimproved vehicle propulsive efficiency, but also to the worldwide effortto reduce vehicle fuel consumption—and thereby to conserve valuableenergy resources.

While the embodiments shown illustrate application generally tofront-wheel assemblies on various vehicles, the embodiments could besimilarly applied to the rear or intermediate wheels of any wheeledvehicle or vehicle trailer. And while the embodiments illustrateddemonstrate shielding applied primarily to the front-most section ofupper wheel assemblies, such shields may be extended to closely coverthe entire upper half of wheels, especially where enhanced streamliningis desired and sensitivity to crosswinds is not important, as can oftenbe the case for powered cycles and motor vehicles. Accordingly, theembodiments should not be limited to the specific examples illustratedand described above, but rather to the appended claims and their legalequivalents.

I claim:
 1. An apparatus for reducing drag on a wind-exposedshaft-shaped member wherein said shaft-shaped member is a component of avehicle, said apparatus comprising: a streamlined tailfin disposed inrotatable attachment to the shaft-shaped member wherein the tailfin mayswivel freely about said shaft-shaped member in response to windsvarying in direction impinging thereon.
 2. The apparatus of claim 1,wherein the vehicle is configured for operation solely as a non-airbornevehicle.
 3. The apparatus of claim 2, wherein the vehicle is configuredfor operation solely as a terrestrial vehicle.
 4. The apparatus of claim3, wherein the vehicle is a cycle.
 5. The apparatus of claim 4, whereinthe vehicle is a bicycle.
 6. The apparatus of claim 5, wherein, further:the shaft-shaped member is a tension member stretched taut along thelength of the tailfin; and the shaft-shaped member is substantiallystraight along the length of the tailfin.
 7. The apparatus of claim 6,wherein the shaft-shaped member is a bicycle wheel spoke.
 8. Theapparatus of claim 1, wherein the shaft-shaped member is a tensionmember stretched taut along the length of the tailfin.
 9. The apparatusof claim 2, wherein the shaft-shaped member is a tension memberstretched taut along the length of the tailfin.
 10. The apparatus ofclaim 3, wherein the shaft-shaped member is a tension member stretchedtaut along the length of the tailfin.
 11. The apparatus of claim 1,wherein the shaft-shaped member is substantially straight along thelength of the tailfin.
 12. The apparatus of claim 2, wherein theshaft-shaped member is substantially straight along the length of thetailfin.
 13. The apparatus of claim 3, wherein the shaft-shaped memberis substantially straight along the length of the tailfin.
 14. A methodfor minimizing drag on a wind-exposed shaft-shaped member wherein saidshaft-shaped member is a component of a vehicle, said method comprising:forming a streamlined tailfin disposed in rotatable attachment to theshaft-shaped member wherein the tailfin may swivel freely about saidshaft-shaped member in response to winds varying in direction impingingthereon; and configuring the tailfin for providing reduced drag on theshaft-shaped member in response to a variable wind impinging thereonwherein said variable wind varys substantially in impinging directionabout said shaft-shaped member during operation of the vehicle.
 15. Themethod of claim 14, wherein the vehicle is configured for operationsolely as a non-airborne vehicle.
 16. The method of claim 15, whereinthe shaft-shaped member is a tension member stretched taut along thelength of the tailfin.
 17. The method of claim 14, wherein theshaft-shaped member is a tension member stretched taut along the lengthof the tailfin.
 18. The method of claim 15, wherein the vehicle isconfigured for operation solely as a terrestrial vehicle.
 19. The methodof claim 18, wherein the vehicle is a cycle.
 20. A method for optimallyreducing drag on a wind-exposed shaft-shaped member wherein saidshaft-shaped member is both a component of a vehicle and is exposed towinds impinging thereon from a plurality of impinging directions asspaced along a major length thereof, said method comprising: forming aplurality of streamlined tailfins disposed in rotatable attachment tothe shaft-shaped member wherein said tailfins may swivel freely aboutsaid shaft-shaped member in response to winds varying in directionimpinging thereon; and configuring the tailfins for each providingreduced drag on a respective section of said shaft-shaped member inresponse to a variable wind impinging thereon wherein said variable windvarys substantially in impinging direction about said respective sectionduring operation of the vehicle.
 21. The method of claim 20, wherein thevehicle is configured for operation solely as a non-airborne vehicle.22. The method of claim 21, wherein the vehicle is configured foroperation solely as a terrestrial vehicle.
 23. The method of claim 20,wherein the shaft-shaped member is a tension member stretched taut alongthe length of the plurality of tailfins.
 24. The method of claim 21,wherein the shaft-shaped member is a tension member stretched taut alongthe length of the plurality of tailfins.